1. Field
This invention relates to means for evacuating undesired bodily secretions of medical patients. It is more particularly directed to medical pumps, notably peristaltic pumps in filtered conduit systems. It is specifically directed to improved procedures for the fluid transfer stage of kidney dialysis treatments.
2. State of the Art
The medical environment has numerous applications for fluid delivery and suction. During surgery, for example, entry sites must have blood or other fluids evacuated. Emergency care personnel must clean a wound properly during care and cleanup. For example, after-surgery complications can cause the endocrine system to overproduce, building pockets of fluid in and around the lungs, or within the peritoneal cavity. In each case, the excess fluid must be removed. This procedure must be accomplished in a mild, gentle manner to avoid tissue trauma or damage to the surrounding area.
Many fluid delivery systems, particularly in a hospital, outpatient, laboratory or home care environment, utilize pumps. Various types of such pumps are constructed with piston, diaphragm, or peristaltic mechanisms. Some such pumps are capable of bi-directional function. While the majority of medical pumps are relied upon for the infusion of fluids, some are applied to evacuation procedures.
Applications of various liquid handling and delivery systems include infusion of blood and blood products such as in hemodialysis; total perenteral nutrition; chemotherapy; hydration maintenance; transfer of samples from one container to another; and administration of medicaments to tissues, organs, the vascular system or other bodily sites. Other applications include pleural therapy, evacuation of wound weepage and other undesirable bodily secretions as well as transfer of peritoneal dialysate solutions. Such infusion and evacuation procedures typically utilize lower volume pumps.
Though some pumps for micro-volume applications are inexpensive enough to be disposable, as illustrated by U.S. Pat. Nos. 5,556,263 and 5,632,606 to Jacobsen et al., virtually all medical pumps, particularly those of higher-volume systems, notably, those used for peritoneal dialysis, are prohibitively expensive for patient acquisition.
The negative pressure necessary to evacuate fluids is typically generated by means of gravity, a bellows-type container, a resilient bladder or a mechanical pump. Representative such means devices disclosed by U.S. Pat. Nos. 3,875,941 to Adair; 3,982,539 to Muriot; and 3,742,822 to Talbert. The device disclosed in U.S. Pat. No. 5,029,580 to Radford et al. incorporates a multi-lumen endotracheal catheter for simultaneous introduction of therapeutic gases under positive pressure and aspiration of undesirable respiratory secretions and gases under negative pressure. Additional lumens may be incorporated for introduction of medication and lavage solutions. Provision may also be made for monitoring pressures, temperatures and catheter tube flow rates. The interaction of negative and positive pressures at the distal (patient) tip of such catheters combined with tip perforations and curvatures results in homogenization of localized secretions and gases, resulting in more efficient aspiration.
Screening at the distal tip of such devices may be accomplished by structure such as those disclosed in U.S. Pat. Nos. 3,308,825 to Cruse; 4,002,170 to Hansen et al.; and 4,068,664 to Sharp et al.
Existing evacuation devices suffer from various disadvantages. Flow rates tend to be either fixed or irregular, and are insufficiently regulated. Flows are typically uni-directional. Costs are prohibitively high for disposability, adversely impacting the ambulatory user. Operation is excessively complicated, unduly limiting the home care user.
There is a need for a low-volume, micro-evacuator device, wherein electronic circuitry enables regulated flow rates in alternate directions of flow in a selected, even adjustable, net-suctioning pattern. This mode of operation would prevent obstruction of the suction catheter and enhance the reliability of secretion flow. There is also a need for an inexpensive high-volume medical pump.
It would also be advantageous for a micro-evacuator device to be constructed (1) unobtrusively to enable ongoing suction of undesired bodily fluids throughout ambulation of a patient; (2) sufficiently inexpensive to be disposable; (3) sufficiently simple for use in a home care environment and/or (4) with a real-time monitor and indicator of catheter pressure and other important variables.
In low-volume applications it is necessary or desirable to provide pump portability to reduce health care costs and enhance patient comfort, convenience, ambulatory productivity and overall lifestyle. For identical reasons it would be desirable to achieve portability for high-volume pumping applications, such as peritoneal dialysis. Current high-volume pumps incorporate bulky, heavy and expensive features such as AC powered liquid warming chambers, alarms for obstruction, volumetric and pressure monitoring, programmable actuation schedules and bidirectional flow. Accordingly, they are generally stationary, and not portable. U.S. Pat. Nos. 4,381,003 and 4,498,900 to Buoncristiani and 5,438,510 to Bryant et al. disclose such elements. There remains a need for a small, light-weight and portable medical pump to support high-volume transfers.
During a typical peritoneal dialysis procedure involving a pump, known as continuous cyclical peritoneal dialysis or CCPD, the pump remains affixed to a power source, and the patient remains attached to the pump for several cycles of infusion and evacuation of dialysate solution throughout the night. The gravity feed/drain approach, known as continuous ambulatory peritoneal dialysis or CAPD, likewise requires patient immobility throughout approximately five such transfers every four to six waking hours involving roughly at least 10 minutes to infuse new dialysate and 20 minutes to drain used dialysate each transfer. There is a need for a medical pump capable of more rapidly transferring high-volumes of dialysate into and out of a patient who may remain ambulatory not only during dialysis but also throughout each transfer procedure.
Presently, both gravity feed and pump methods of performing peritoneal dialysis normally involve drainage of used solution from the peritoneum into an unused receptacle for later disposal. Clean, unused solution is then introduced into the peritoneum from a solution reservoir. These procedures, typical examples of which are illustrated by U.S. Pat. Nos. 3,620,215 to Tysk; 4,396,382 to Goldhaber and 4,412,917 to Ahijopalo, require the use of two separate solution containers. Such procedures presuppose a series of valve or clamp openings and closings in a defined sequence to ensure that solution is directed in accordance with protocol, illustrative of which is FIG. 4 of U.S. Pat. No. 4,239,041 to Popovich et al.
It is important that any pump transfer set provide for facile, clean connection and disconnection of the dialysate containment system to the indwelling catheter tube, whereby to minimize the potential for peritonitis. When an ambulatory patient completes a transfer of dialysis solution through a stationary pump, the patient is normally disconnected from the pump at the indwelling tube. The patient is thereby permitted to move about freely, until being reconnected to continue with the next transfer procedure. Each such exchange exposes a patient to potential contamination. Typical precautions against contamination involve wearing a face mask, closing windows and doors and turning off air conditioning in rooms or vehicles in which exchanges are to take place. These expedients are not entirely effective, and there thus remains a need for an improved arrangement, whereby to minimize this mode of patient exposure.
Though unused dialysis solution is sterile, organic particles and air bubbles are typically carried by the solution. Air bubbles introduced to the patient are known to cause severe muscle pains in the shoulders and chest, until the air diffuses into the surrounding body tissues. Some incidence of non-bacterial peritonitis is known to be associated with the organic materials carried by dialysis solution. An air and particle filter for use in a gravity-feed system is disclosed by U.S. Pat. No. 4,239,041 to Popovich et al. U.S. Pat. No. 4,311,587 to Nose et al. discloses a system in which a filter for use with a pressurized source of fresh dialysate solution is associated with a check valve constructed to permit flow only away from the filter. U.S. Pat. No. 4,488,961 to Spencer discloses a housing for maintaining a filter element in a filtering position during fluid infusion and in a free-flow position during fluid withdrawal. Filters preventing passage of bacteria prevent rapid gravity-flow and are only practical for use with pumps, not gravity flow CAPD. There remains a need for a practical system for screening out air bubbles and filtering particulate matter from fresh dialysate. There is a further need for such a filter to protect against microbial migration to the peritoneal cavity during an exchange of single- or multiple-bag dialysate containment systems.